JPH0994868A - Apparatus for measuring amount of feeding of material for extrusion molding machine and apparatus for controlling amount of extrusion for extrusion molding machine using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately and rapidly measure the amt. of feeding of a material per unit time into an extrusion molding machine. SOLUTION: A metering part 33 measures the wt. of a hopper for feeding a material into an extrusion molding machine and outputs it to a controlling part 35. A part 37 for measuring the no. of rotation outputs the no. of rotation of the main screw of the extrusion molding machine to the controlling part 35 and outputs a pulse on every rotational cycle of the main screw to the controlling part 35. The controlling part 35 takes a measured data from the metering part 33 on every pulse and operates the amt. of feeding (the amt. of consumption) of the material per unit time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material supply amount measuring device for an extrusion molding machine and a discharge amount controlling device for an extrusion molding machine using the same, which contributes to uniform quality of extruded products from the extrusion molding machine. And a discharge amount control device.

[0002]

2. Description of the Related Art An extrusion molding line for extruding a long product such as a plastic pipe or a laminated product such as a plastic sheet has an extruder 1 and a take-up machine 3 as shown in FIG.
Are connected to each other, and the molded product 5 obtained by extruding the melted plastic material from the extrusion molding machine 1 is drawn and molded by the drawing machine 3. Then, in the extrusion molding machine 1, a cylinder 9 containing the main screw 7 is placed on a molding machine base 11, and on the molding machine base 11, an extrusion motor 13 for rotationally driving the main screw 7 and the extrusion motor 13 are installed. A rotation speed detection sensor 15 for detecting the rotation speed is arranged.

A hopper 17 for supplying a plastic material into the cylinder 9 is arranged on the cylinder 9, and a material storage section 19 filled with a plastic material to be replenished in the hopper 17 is arranged above the hopper 17. ing. As shown in FIG. 4, a weighing unit 21 for measuring the weight of the hopper itself is connected to the hopper 17, and weighing data is output to the control device A (not shown in FIG. 4) via a cable or the like. It is like this. Therefore, the hopper 17 is a material supply unit called a weighing pot or a weighing hopper.

When the remaining amount of the plastic material in the hopper 17 becomes small, the shutter 19a of the material storage unit 19 (a little changed from the one shown in FIG. 3) is opened under the control of the controller A, and the plastic material is removed. Hopper 17
It is designed to be replenished inside. However, there is also a case where the shutter 19a is manually opened to replenish the plastic material. Reference numerals 23 and 25 in FIG. 3 denote a temperature sensor and a pressure sensor arranged in the cylinder 9.

In such an extrusion molding line, the plastic material supplied from the hopper 17 to the cylinder 9 is heated and melted, and the main screw 7 is rotationally driven to form a molded product from a die (not shown) at the tip of the cylinder 9. Extruded as 5. The extruded molded product 5 is taken up by the take-up roller 29 which is rotationally driven by the take-up motor 27 to be commercialized.

The rotation speed of the take-up motor 27 is detected by a rotation speed detection sensor 31 similar to the sensor 15, and is output to the control device A. The control device A controls the weighing data from the weighing unit 21, the rotation speed detection sensors 15 and 3,
The rotation speed signals of the extrusion motor 13 and the take-up motor 27 from 1 are taken in, and the rotation speeds of the motors 13 and 27 are controlled so that the ejection volume of the extruded molded product 5 per unit time becomes uniform.

Conventionally, in such an extrusion molding line, in order to make the discharge amount from the cylinder 9, that is, the volume of the extruded molded product 5 uniform and to keep the quality of the product constant, for example, as shown in FIG. , The material from the measurement period (extrusion period) after the material is put into the hopper 17, and the maximum and minimum values (measured by the measuring unit 21) of the plastic material in the hopper 17 at the beginning and end of the measurement period. While measuring the supply amount (consumption amount), the volume of the molded product 5 to be extruded is calculated from the relationship between the measurement result and the extrusion cross-sectional area of the die and the like, and the extrusion motor 13 is operated so as to bring it closer to the desired discharge amount. The ejection rate and the take-up speed of the take-up motor 27 are controlled to control the discharge amount.

[0008]

However, the above-mentioned conventional material supply amount measuring method and discharge amount controlling method in the extrusion molding line have the following disadvantages. That is, the plastic material in the hopper 17 is
While the main screw 7 rotates, the plastic material extruded from the extrusion molding machine 1 falls by its own weight according to the reduction amount and is supplied into the cylinder 9, but the material of the cylinder 9 is rotated during the rotation of the main screw 7. The ridges 7a of the main screw 7 regularly pass near the charging port 9a (fourth
See figure).

Then, when the crest portion 7a of the main screw 7 passes near the material inlet 9a of the cylinder 9, the crest portion 7a of the main screw 7 pushes up the hopper 17 and the measured weight is temporarily increased. It becomes reduced and the change of the measured weight with time is accompanied by vibration. for that reason,
The hopper weight into the cylinder 9 measured by the weighing unit 21 does not change like the diagonal straight line in FIG. 5 when the material is not replenished from the material storage unit 19, and is indicated by the broken line of the waveform in FIG. As shown in the figure, since it decreases with vibration, a large error is likely to occur when measuring the material supply amount in a short section measurement, and it has to be measured in a relatively long period, for example, in a few minutes at the shortest. It was difficult to quickly measure the weight of the hopper, and it was also difficult to make the quality of the molded product 5 uniform and to control the change of the thickness quickly.

[0010] Of course, although not shown, the auxiliary material supply mechanism for supplying a constant amount of material is hopper-processed by a filter to process the material supply amount change data per unit time obtained from the measuring unit 21 by a filter. 1
There is also an attempt to obtain an accurate material supply amount by providing it between the No. 7 and the main screw 7. However, the method of processing the measurement data from the measuring unit 21 by software is to apply a first-order lag filter to the measurement data to make the oscillatory change uniform, but a first-order lag filter with a sufficiently long time constant is used. It is necessary to use it, and after all, it is difficult to quickly respond to fluctuations in measurement data.

There is also a method of equalizing vibrational changes by the moving average method, but since the filter effect is not uniform with respect to frequency in the moving average method, when the rotation of the main screw 7 fluctuates, There was a problem that the filter effect was reduced. Further, the structure in which the auxiliary material supply mechanism is provided between the hopper 17 and the main screw 7 has a problem that the structure is complicated and the cost is easily increased significantly. Therefore, the material supply amount measuring device capable of accurately and quickly measuring the change in the material supply amount to the extruder 1 and the rotation speed of the extrusion motor 13 of the extruder 1 are controlled to control the discharge amount. It has been desired to provide a discharge amount control device that can achieve stabilization.

The present invention has been made under such circumstances, and provides a material supply amount measuring device capable of accurately and quickly measuring a change in the material supply amount of an extruder. Further, the present invention provides a discharge amount control device capable of stabilizing the discharge amount from the extruder.

[0013]

In order to solve such a problem, a material supply amount measuring apparatus according to the present invention is a measuring unit for measuring the weight of a material supply unit for supplying a material to the screw side of an extruder. And a rotation speed measuring unit for measuring the rotation speed of the screw, and N (a positive integer, the same applies hereinafter) based on the measured rotation speed, from the measurement data taken in every rotation cycle, to the screw side per unit time. And a control unit for calculating the material supply amount.

Moreover, the material supply amount measuring device of the present invention is
It is also possible to form the control unit so as to acquire the measurement data for every plural rotation cycles of the screw. Further, the discharge amount control device according to the present invention, a weighing unit for measuring the weight of the material supply unit for supplying the material to the screw side of the extruder, a rotation speed measurement unit for measuring the rotation speed of the screw, and The material supply amount per unit time to the screw side is calculated from the measurement data taken in every N rotation cycles based on the measured rotation speed, and the control signal obtained from this calculation result is
At least a control unit that controls the discharge amount of the screw that is output to the rotation drive motor side and is extruded from the extruder.

Further, in the discharge amount control device of the present invention, it is possible to form the control part so as to take in the measurement data at every plural rotation cycles of the screw. Further, the discharge rate control device of the present invention is provided with a speed command unit for speed-controlling at least the screw rotation drive motor by a control signal from the control unit, and the control unit outputs the next control signal until the next control signal is output. The speed command unit may be formed so as to continuously output the signal.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing one embodiment of a material supply amount measuring device and a discharge amount control device using the same according to the present invention. The configuration of the extrusion molding line is the same as that shown in FIG. FIG.
3, the weighing unit 33 corresponds to the weighing unit 21 of FIG. 3 and is connected to the control unit 35. The weight of the hopper 17 as a material supply unit is hung and the weight is measured and converted into an electric signal. , To the control unit 35.

Since the weight of the hopper 17 does not change, the weight of the hopper 17 is measured continuously or at a predetermined timing so that the change in the measured data causes the amount of material supplied from the hopper 17 to the main screw 7 side (consumption). Quantity). The rotation speed measurement unit 37 includes the main screw 7
Which is a rotation speed detection sensor for measuring the rotation speed of the
5, which is connected to the rotation speed detection sensor 15 or 3 of FIG.
As in the case of No. 1, it is formed of a tacho-generator and a rotary encoder and outputs the rotation speed of the main screw 7 to the control unit 35.

Moreover, the rotation speed measuring section 37 also has a function of outputting one pulse to the control section 35 every one rotation cycle of the main screw 7. However, the pulse for each one rotation cycle is synchronized with the rotation cycle of the main screw 7.
Any number of pulses will do. The control unit 35 takes in the number of revolutions of the main screw 7 from the revolution number measuring unit 37 and a pulse synchronized with the main screw 7, retrieves the measurement data from the measuring unit 33 in synchronization with this pulse, and retrieves the retrieved measurement data. It has a function of calculating the amount of material supplied to the cylinder 9 per unit time by measuring the weight change for a predetermined period, for example, one second or several seconds, or at most several tens of seconds.

In the material supply amount measuring device thus constructed, as shown in FIG. 4, the ridge portion 7a of the main screw 7 passes near the material input port 9a of the cylinder 9 so that the measured data of the hopper weight can be measured, for example. When it occurs like the waveform of 2, the first hopper weight measurement is performed at an arbitrary starting point of one rotation cycle of the main screw 7, and then the second hopper weight measurement is performed after one rotation cycle of the main screw 7. I do. The measurement points of the first and second hopper weights are, for example, from the waveform of the hopper weight measurement waveform shown in FIG. 2, between two points from mountain to mountain, two points from valley to valley, and from valley to mountain. It will be between two midpoints.

From the above measurement, the material supply amount (consumption amount) per time required for one rotation of the main screw 7 can be obtained by calculating the difference between the weight of the first hopper and the weight of the second hopper. Therefore, even if the material supply amount decreases and fluctuates due to vibration, the measurement data at almost the same position is taken in every revolution of the main screw 7, and the material supply amount can be measured almost accurately. It is possible to measure in a short period unit such as every one revolution of the main screw 7 or every few revolutions, and it is possible to perform an accurate measurement per unit time such as every 1 to several seconds.

Moreover, since the fluctuation of the hopper weight occurs in synchronization with the main screw 7 due to this rotation, the fluctuation is usually accompanied by the vibration fluctuation of the waveform as shown in FIG.
By taking the measurement data once per one rotation cycle of the main screw 7, the measurement error when the peak portion 7a of the main screw 7 passes under the hopper 17 can be eliminated, and the material supply amount can be measured almost accurately. Is.

By the way, in the above-described material supply amount measuring apparatus of the present invention, the rotation speed measuring unit 37 outputs one pulse for each one rotation cycle synchronized with the rotation of the main screw 7.
However, the control unit 35 is configured to output a pulse to the control unit 35 every plural rotation cycles of the main screw 7, and the control unit 35 fetches the measurement data for each plural rotation cycle of the main screw 7, A configuration for calculating the amount of material supplied per time is also possible. In short, it suffices to capture the measurement data every N rotation cycles in synchronization with the rotation cycle of the main screw 7.

As described above, even when the measurement data is taken in every plural rotation cycles of the main screw 7, since the unit time is extremely short compared with the conventional measurement period shown in FIG. 5, an accurate supply amount can be obtained. It is possible. Further, as compared with the configuration in which the measurement data is captured at every rotation cycle of the main screw 7, the measurement timing (sampling cycle) becomes longer, so high speed calculation is not required and the calculation circuit or software becomes lighter. Even if 7 rotates at high speed, there is an advantage that the calculation can catch up.

However, the plurality of rotation cycles are preferably several rotation cycles from the viewpoint of control accuracy, and at most about 20 rotation cycles. In the above method, when N is set to a plurality and N times of N rotation cycles are fixed, when the number of rotations of the main screw 7 largely changes, the sampling cycle also largely changes.
Therefore, when it is desired to keep the sampling period constant, the multiple rotation period (N) is N = {main screw rotation number (times / second)} / {sampling cycle (times / second)}, and N is made variable. As a result, even if the main screw rotation speed changes significantly, it is possible to obtain an accurate supply amount by keeping the sampling cycle constant.

Next, a discharge amount control device using the above-mentioned material supply amount measuring device will be described. This discharge amount control device,
The measuring unit 33, the control unit 35, and the rotation speed measuring unit 3 described above.
7, the speed command unit 39, the pushing motor 41 and the take-up motor 43 are further added, and the function of the control unit 35 is expanded. That is, the speed command unit 39
A speed command signal for rotationally driving the pushing motor 41 and the pulling motor 43 similar to the pushing motor 13 and the pulling motor 27 in FIG. 3 is output by a control signal as a rotation speed signal based on the calculation of the control unit 35. At the same time, it has a latch function or a memory function that continuously outputs the same speed command signal to the pushing motor 41 and the take-up motor 43 unless the control unit 35 outputs the next rotation speed signal.

The control unit 35, based on the rotation speeds of the pushing motor 41 and the take-up motor 43 from the rotation speed measuring unit 37,
A rotation speed signal for controlling the rotation of these to a desired rotation speed is output to the speed command unit 39. Moreover, the control unit 35
Calculates the supply amount of the material to the cylinder 9 for each rotation of the main screw 7 as described above, and from the calculation result,
It has a function of calculating the volume of the molded product 5 to be extruded, and outputting to the speed command section 39 as a control signal a rotation speed signal corrected with data such that the difference from the desired or set volume is small. There is.

In such a discharge amount control device of the present invention,
Since the rotation speed signal of the extrusion motor 41 or the take-up motor 43 is output as a control signal from the accurate supply amount of the material, the discharge amount of the molded product 5 extruded from the extrusion molding machine 1 by the main screw 7 or the take-up roller 29. Can be accurately controlled, a molded product 5 having a uniform volume can be manufactured, and even if the discharge amount is changed and controlled, the molded product 5 can be quickly and easily stabilized. Moreover, since the speed command unit 39 having the latch function is provided, the control unit 35
Until the next control signal is output, the control signal is continuously output to the extrusion motor 41 and the take-up motor 43,
Smooth rotation of the pushing motor 41 and the take-up motor 43 can be ensured.

However, in the discharge amount control device of the present invention,
The object of the present invention can be achieved without necessarily providing the speed command unit 39, and in the configuration in which the speed command unit 39 is not provided,
The control unit 35 may be formed so as to output a speed signal to the pushing motor 41 or the take-up motor 43 side. Furthermore, the configuration is not limited to the case where both the pushing motor 41 and the take-up motor 43 are controlled, and a configuration in which at least the pushing motor 41 is controlled is also possible. Further, in the discharge amount control device of the present invention,
It goes without saying that a configuration in which the material supply amount is calculated from the measurement data taken in every plural rotation cycles of the main screw 7 is also possible.

By the way, in the discharge amount control device of the present invention,
The volume of the molded product 5 extruded is calculated from the calculation result of the supply amount of the material to the cylinder 9, and the rotation speed signal is output from the control unit 35 so that the volume becomes uniform or becomes a desired volume. However, even if the amount of material supplied to the cylinder 9 is measured almost accurately and quickly, there is a slight time delay until the molten plastic material is extruded from the cylinder 9 by the rotation of the main screw 7, but the so-called Since it is sufficient to control the pushing motor 41 and the take-up motor 43 in consideration of the dead time, the discharge amount can be controlled almost accurately. In each of the above-described embodiments, the extruder 1 having one main screw 7 has been described, but the present invention is applicable to an extruder using a plurality of screws.

[0030]

As described above, the material supply amount measuring device of the present invention is based on the measured rotation speed of the screw measured by the rotation speed measurement unit by measuring the weight of the material supply unit of the extruder by the measuring unit. The control unit takes in the measurement data for each cycle of one rotation or more and calculates the material supply amount to the screw side of the extrusion molding machine, so the change in the material supply amount to the extrusion molding machine is accurate. And it becomes possible to measure quickly. Moreover, in the configuration in which the control unit is formed so as to calculate the material supply amount by taking the measurement data for every plural rotation cycles of the screw, there is a margin in the calculation while maintaining the measurement accuracy of the material supply amount. It can also be used for high speed rotation control. Further, the discharge rate control device for an extruder according to the present invention measures the weight of the material supply section of the extruder at the measuring section, and the number of rotations of 1 or more based on the measured rotation speed of the screw measured by the rotation speed measurement section. At each cycle, the control unit fetches the measured data and calculates the material supply amount to the screw side of the extruder, and at least the control signal obtained from the calculation result at the control unit is supplied to the screw rotation drive motor side. Since the output amount is output to the extruder and the discharge amount of the extruder is controlled, the discharge amount from the extruder is made uniform, the quality of the extrusion molded product can be stabilized, and the configuration is not complicated. And
In the discharge amount control device, the control unit is formed so as to calculate the material supply amount by fetching the measurement data for every plural rotation cycles of the screw, so that the discharge amount can be controlled with a margin in the calculation. Is. Further, in the discharge rate control device, in the configuration in which the speed command unit having a latch function controls the speed of at least the screw rotation drive motor, smooth rotation of the screw can be ensured. Contributes to stabilization.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a material supply amount measuring device and a discharge amount control device according to the present invention.

FIG. 2 is a diagram for explaining the operation of the embodiment shown in FIG.

FIG. 3 is a diagram illustrating an extrusion molding line.

FIG. 4 is a diagram illustrating a conventional material supply configuration.

FIG. 5 is a diagram illustrating a conventional material supply amount measuring operation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Extrusion molding machine 3 Pulling machine 5 Molded product 7 Main screw (screw) 9 Cylinder 11 Molding machine stand 13,41 Extrusion motor 15,31 Rotation speed detection sensor 17 Hopper (material supply part) 19 Material storage part 19a Shutter 21, 33 metering unit 23 temperature sensor 25 pressure sensor 27, 43 take-up motor 29 take-up roller 35 control unit 37 rotational speed measuring unit 39 speed command unit A control device

Claims (5)

[Claims] 1. A weighing unit that measures the weight of a material supply unit that supplies a material to the screw side of an extruder, a rotation speed measurement unit that measures the rotation speed of the screw, and N (based on the measured rotation speed). (A positive integer) A control unit for calculating the material supply amount to the screw side from the measurement data acquired for each rotation cycle, and a material supply amount measuring device for an extruder, comprising: 2. The control unit fetches the measurement data at every plural rotation cycles of the screw.
The material supply amount measuring device of the extruder described. 3. A weighing section for measuring the weight of a material supply section for supplying a material to the screw side of an extruder, a rotation speed detection section for measuring the rotation speed of the screw, and N (based on the measured rotation speed). (A positive integer) The material supply amount to the screw side is calculated from the measurement data captured for each rotation cycle, and the control signal obtained from this calculation result is output to at least the rotation drive motor side of the screw to output the control signal. A discharge amount control device for an extrusion molding machine, comprising a control unit for controlling a discharge amount extruded from the extrusion molding machine. Wherein said control unit, according to claim 3 in which takes in the measurement data for each of a plurality of times <br/> rotation period of the screw
Discharge amount control device of the described extruder. 5. A speed command unit for speed-controlling at least the rotary drive motor of the screw according to the control signal from the control unit, the control signal being output until the next control signal is output from the control unit. The discharge amount control device for an extruder according to claim 3 or 4, further comprising a speed command unit that continuously outputs the speed command unit.